Climate control poses a severe challenge for environmentally friendly vehicles, including battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), extended range electric vehicles (EREVs), and even hybrid electric vehicles (HEVs). Cabin heating, depending on the size of the vehicle and the environmental conditions, typically requires 3.2 to 6.5 kW of battery power at the ambient of −10° C. (a nominal design point for heating) to meet transient and steady state comfort requirements. For the larger sized electric vehicles of various genres (xEV), the required electrical power for heating from the traction battery may be even greater. The battery power used to generate the heating, either through a heat pump or direct resistive heating, leads to dramatic decrease in the driving range of xEVs. It is estimated that the driving range of a BEV can be reduced by 20-50%, depending on the drive cycle.
Electric heaters generally consume a significant amount of energy stored in the traction battery. Range reduction is a widely recognized shortcoming of the technology. In BEVs and PHEVs, a common heating technology is a PTC heater (Positive-thermal-coefficient heater) that is configured to be part of an air circuit or coolant circuit.
It is also known that hot coolant storage has been used to assist with cabin heating. In these systems, an electric heater feeds heat energy to the coolant in an insulated storage tank while the vehicle is stationarily connected to an external electric power source. The heat is then stored in the coolant for later use. While coolant energy storage can help reduce the load on the traction battery while in operation, it has a limited capacity to sustain heating and is thus insufficient for extended trips.